From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-3.6 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE, SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id F2817C2D0EA for ; Wed, 8 Apr 2020 15:57:26 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id C82DB20769 for ; Wed, 8 Apr 2020 15:57:26 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="HmTprzgO" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729771AbgDHP5Z (ORCPT ); Wed, 8 Apr 2020 11:57:25 -0400 Received: from bombadil.infradead.org ([198.137.202.133]:50572 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729506AbgDHP5Z (ORCPT ); Wed, 8 Apr 2020 11:57:25 -0400 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20170209; h=In-Reply-To:Content-Type:MIME-Version :References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=I046T5NYEXXComMYfFLIbN9Cazs44K1u/PrUj66bzFg=; b=HmTprzgO5Copd6ZM1O4M8f7lqo f8qIXu5dpV028o2e5sdn8xVqUUhTBYMQR+GMGt+hJ1IJecOoARrlIKWLg415az9UIqcusPvyl8uz+ miEvVeFzuoWIwXHmxbpQn9kXE0Zas5RB8foRfxDbRqXEE1JvZqQnSEP/BR14QJ8RGny6GZPORiuzW 3zPAsgt0GKmqaDA5wfUroIwZzNwWqa5Oyt6/WJuuqfiC3vdwvl5PUdye6VavZzTWOkYtVAE4iIArN cvABGFvjeu//zLY3E1yYaVOEUFd/poCBrOiG2T2x6VW/3y6aif4Ofo8fqQH8SGVdD4lSSL/d/1spP ewOsulXA==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=noisy.programming.kicks-ass.net) by bombadil.infradead.org with esmtpsa (Exim 4.92.3 #3 (Red Hat Linux)) id 1jMD4r-00074a-PV; Wed, 08 Apr 2020 15:57:21 +0000 Received: from hirez.programming.kicks-ass.net (hirez.programming.kicks-ass.net [192.168.1.225]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id BD0BA300130; Wed, 8 Apr 2020 17:57:19 +0200 (CEST) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id AE5DA2BB02700; Wed, 8 Apr 2020 17:57:19 +0200 (CEST) Date: Wed, 8 Apr 2020 17:57:19 +0200 From: Peter Zijlstra To: Jessica Yu Cc: linux-kernel@vger.kernel.org, Thomas Gleixner , keescook@chromium.org, Josh Poimboeuf , Miroslav Benes Subject: Re: [PATCH v2] module: Harden STRICT_MODULE_RWX Message-ID: <20200408155719.GQ20730@hirez.programming.kicks-ass.net> References: <20200403171303.GK20760@hirez.programming.kicks-ass.net> <20200408153249.GA26619@linux-8ccs> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200408153249.GA26619@linux-8ccs> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Apr 08, 2020 at 05:32:49PM +0200, Jessica Yu wrote: > +++ Peter Zijlstra [03/04/20 19:13 +0200]: > > > > We're very close to enforcing W^X memory, refuse to load modules that > > violate this principle per construction. > > > > Signed-off-by: Peter Zijlstra (Intel) > > --- > > kernel/module.c | 25 +++++++++++++++++++++++++ > > 1 file changed, 25 insertions(+) > > > > --- a/kernel/module.c > > +++ b/kernel/module.c > > @@ -2044,9 +2044,29 @@ static void module_enable_x(const struct > > frob_text(&mod->core_layout, set_memory_x); > > frob_text(&mod->init_layout, set_memory_x); > > } > > + > > +static int module_enforce_rwx_sections(Elf_Ehdr *hdr, Elf_Shdr *sechdrs, > > + char *secstrings, struct module *mod) > > +{ > > + const unsigned long shf_wx = SHF_WRITE|SHF_EXECINSTR; > > + int i; > > + > > + for (i = 0; i < hdr->e_shnum; i++) { > > + if ((sechdrs[i].sh_flags & shf_wx) == shf_wx) > > + return -ENOEXEC; > > + } > > + > > + return 0; > > +} > > Just to clarify, did we want to enforce this only when > CONFIG_STRICT_MODULE_RWX=y? Because here it's still in the > CONFIG_ARCH_HAS_STRICT_MODULE_RWX block. > > Unfortunately, when we add module_enforce_rwx_sections() in the > CONFIG_STRICT_MODULE_RWX block, we'll need two empty stubs, one for > !CONFIG_ARCH_HAS_STRICT_MODULE_RWX and one for !CONFIG_STRICT_MODULE_RWX. > > This is because the CONFIG_STRICT_MODULE_RWX block is currently nested > within ARCH_HAS_STRICT_MODULE_RWX :/ Yeah, so the primary reason it's under that ARCH_HAS thing is indeed the mess and the extra stub required (I'm a lazy sod at times). I then rationalized this decision to myself that having it under ARCH_HAS give a more consistent module loading behaviour. But I really don't care too much, my most my .config's have CONFIG_MODULE=n, and the ones that do not very much have the STRICT_RWX set. Put it where you think it's best. Thanks!